Here just a few basic tips:
1. Villains are people too, so drop the every villain is a psychopath mentality. Sorry, but not every villain is born as pure evil. Life shapes a person's psyche, so perhaps you could include a moment or series of events that turned your character from good to 'evil'.
2. If you have a psychopath in your story, then at least do some research regarding mental illness to understand that type of behavior. Watching a bunch of action movies is not the right kind of research.
3. Villains are at different levels of evil. Some are ruthless businessmen who want nothing more than to destroy their competition via sabotage. Some are bullies who are out to torment weaker kids because the bully has a parent at home that torments him or her. Some are crooked politicians who look the other way when a company dumps a bunch of chemicals into the drinking water supply of some poor community.
4. A villain could have a hobby. Maybe they enjoy cooking or fishing. Remember that villains are human.
5. Villains can be non-human. They can be aliens or robots or demons. However, develop the 'why' portion of their evilness.
These are just a few tips you can use for your villain character development.I'll have more villain stuff for you tomorrow.
TonyDoug Wright is the owner and editor of Champion City Comics. His webcomics include Dr Death vs The Zombie, The End of Paradise, The Red Devil, and Day 165.